The present invention relates in general to weaving looms and, specifically, to a weaving loom of the shuttleless type in which a pick of weft yarn is shot into the shed of warp yarns by a jet stream of fluid under pressure such as, typically, compressed air. More specifically, the present invention is concerned with a fluid supplying and discharging apparatus for use in a weaving loom of the particular type.
A conventional fluid supplying and discharging apparatus of a shuttleless weaving loom has ordinarily incorporated therein an intermittent-motion flow control valve which is located upstream of a fluid discharge nozzle and which is operated to alternately open and close in synchronism with the weaving operation of the loom. When the loom in operation is brought to a stop, the control valve is automatically closed and cuts off the flow of fluid to the fluid discharge nozzle from the source of the fluid so that the fluid discharge nozzle ceases ejection of the fluid provided the loom is stopped with a proper timing, viz., at an instant intervening between termination of a weft shooting cycle and an instant at which the subsequent weft shooting cycle is to start. If, however, it happens that the loom is stopped during a weft shooting cycle in which fluid is being ejected from the fluid discharge nozzle, the flow of the fluid which has been passed through the control valve by the point of time at which the control valve is closed is beyond the control of the valve and is allowed out of the discharge nozzle into the shed of warp yarns. This not only results in a waste of the pressurized fluid and is therefore objectionable from an economical point of view but invites a problem in that the weft yarn which is kept entrained on the jet stream of the fluid issuing from the fluid discharge nozzle and which is thus kept taut for an extended period of time after the loom is stopped is subject to a danger of breakage. These problems could be avoided if a flow shut-off valve adapted to automatically close in response to stoppage of the loom is provided anterior to the fluid discharge nozzle so that the flow of the fluid which has been passed through the intermittent-motion flow control valve located upstream of the fluid discharge nozzle is cut off upstream of the nozzle immediately when the loom is brought to a stop. When the loom is to be started from the rest condition, the flow shut-off valve is opened and the first pick of weft yarn is inserted into the weaving shed of the loom by the aid of a jet stream of the fluid which is continuously discharged from the fluid discharge nozzle by manually operating the control valve. Because, in this instance, the flow shut-off valve located upstream of the nozzle is kept open, the pick of the weft yarn entrained on the jet stream of the fluid issuing from the nozzle is subjected to a forceful tension until insertion of the first pick of weft yarn by manual operation is complete. The weft yarn is thus not only subject to the danger of being broken as in the case of the previously described prior-art apparatus but is forced to untwist and loose its tensile strength if the weft yarn is a spun yarn.
The prior-art fluid supplying and discharging apparatus of the previously described character has a modified version in which a fluid storage chamber is provided between the intermittent-motion flow control valve and the source of the fluid under pressure. The fluid storage chamber has a capacity adapted to store therein a predetermined volume of fluid to be consumed in each weft shooting operation and is operative to periodically deliver the predetermined volume of fluid to the fluid discharging nozzle via the intermittent-motion flow control valve during each of the weft inserting cycles. The provision of the fluid storage chamber is thus useful for limiting the volume of the fluid to be discharged from the fluid discharge nozzle after the loom is brought to a stop during a weft inserting cycle. When weaving operation is to be reopened with the loom equipped with a fluid supplying and discharging apparatus using such a fluid storage chamber, the loom is first driven to operate in normal condition until the fluid storage chamber is completely filled with the fluid supplied from the fluid source. The loom is thereafter operated on a reverse course until the loom restores the initial condition ready to have the first pick of weft yarn shot into the weaving shed. The control valve downstream of the fluid storage chamber is then opened by manual operation for shooting the first pick of weft yarn into the weaving shed by the aid of the fluid which has been stored in the fluid storage chamber. Let alone the numerous steps which must thus be taken for shooting the first pick of weft yarn from the fluid discharge nozzle, a problem is encountered in that the volume of the fluid stored in and delivered from the fluid storage chamber is insufficient for enabling the pick of weft to be shot into the weaving shed with certainty by manual operation.